This invention relates to a process for recovering oil from coal fines that are agglomerated or blended with heavy oil.
Oil agglomeration of coal fines is generally practised using high rank coals and high quality oils as feedstock. The agglomerated low ash and low moisture product can be subjected to thermal treatment to recover the oil. For high quality, i.e. low boiling, oils, it is possible to recover almost 100% of the oil used. Methods of recovering light oils from agglomerates are described in U.S. Pat. Nos. 4,415,335, issued Nov. 15, 1983 to Mainwaring et al. and 4,396,396, issued Aug. 2, 1983 to Mainwaring.
It is also known to use low quality (i.e. heavy) oil in the agglomeration process. Canadian Patent No. 1,216,551 (Ignasiak), issued Jan. 13, 1987, is directed to a method for agglomerating subbituminous coal using heavy oil. In such processes, large quantities of heavy oil in the order of 10-50% of the weight of the coal, are used. U.S. Pat. No. 4,854,940 (Janiak et al. ) , issued Aug. 8, 1989, describes a method for separating distillable hydrocarbons from agglomerated subbituminous coal by contacting the agglomerates with steam or nitrogen at temperatures between 250.degree.-350.degree. C. However, this results in recovery of only about 25-40% of the heavy oil. Further, the heavy oil recovered using this method is not upgraded to lighter, more valuable oils, due to the relatively low temperatures employed. It would be economically desirable to be able to recover more of the heavy oil used, particularly in the form of lighter, distillable oils.